Summary of Significant Accounting Policies - Project Development Costs (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Accounting Policies [Abstract] | ||
| Product development cost included in other long-term assets | $ 2,355 | $ 1,524 |
| X | ||||||||||
- Definition Capitalized Project Development Costs, Noncurrent No definition available.
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| X | ||||||||||
- References No definition available.
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